The present invention relates to a system for image processing and deals more particularly with a system for automatically locating patterns.
Digital image processing is widely used in many industrial applications for locating articles during automated manufacture and directing equipment to operate on those articles. One example is a wire bonding application. Wire bonding describes the process of bonding discrete wires to an integrated circuit chip. Digital image processing can be used to locate the chip, to locate the wire on a chip, and to direct the wire bonder to bond the wire to the appropriate location on the chip.
In any automated manufacturing application including the wire bond application, the first procedure employed by the operator is to train the image processing system on a pattern on a chip. The pattern may be thought of as an object. This is done in a wide variety of ways including automatic and manual procedures. The training process creates a standard template or kernel that can be later used to locate the object or pattern within an image. In most commercial systems after the standard template is trained, the image processing system uses a pattern recognition technique to locate the same object within subsequent images and performs predetermined tasks. If during a production run the system fails to locate the object within an image of a manufactured part with the standard template, the system will initiate an operator assist call. An operator assist call is a warning signal that the image processing system was unable to locate the object in the manufactured part with the standard template. The operator then manually determines whether there is a failure, or whether the manufactured part is valid and the vision system failed. If the problem was caused by a valid manufactured part that has a substantial difference in appearance from the original part, the operator must manually direct the system to the correct location.
If an operator is unable to immediately attend to the alarm the system will stop operation. With the ever increasing output requirements for manufacturing systems any delays in production can be costly. Therefore, a need has arisen to solve the problem of unnecessary operator assist calls.
One aspect of the present invention provides for a method of locating an object within a series of images including providing a first template representative of an object within a standard image. The first template is applied to an image within the series to locate the object. If the first template is unable to locate the object within the subsequent image, another template is applied to determine if a match exists.
It is recognized that a variety of pattern recognition techniques could be used in applying the present invention. These pattern recognition techniques include but are not limited to binary vector correlation, gray scale vector correlation, and gray scale correlation. It is also recognized that the template can be provided in a number of ways, both automatic and manual. The training methods include but are not limited to techniques that involve simulated annealing, random sampling, subsampling, equidistant sampling along edges or sampling on a coarse grid.